Single-Atom Magnets on Thermally Stable Adsorption Sites: Dy on NaCl(100)

We report magnetic bistability in single Dy atoms on NaCl(100) thin films. Individual Dy atoms substituting Na at the surface of the NaCl layer are thermally stable up to at least 300 K, display 4f^{9} occupancy, out-of-plane easy magnetization axis, and long spin relaxation time T_{1} of about 10 s at 2.5 K; therefore, they are the first single-atom magnet on a thermally stable adsorption site. Dy atoms adsorbed onto the Cl and bridge sites display 4f^{10} occupancy. Dy on top-Cl exhibit magnetic hysteresis and a T_{1} of 550 s at 0.3 T and 2.5 K. The observed slow magnetic relaxation of Dy on both adsorption sites introduces NaCl as an effective platform for single-atom magnets.